A method for forming a three-dimensional object, and a three-dimensional printer that form a three-dimensional object by extruding build material such as inks and depositing layers of the build material have been known. For example, in a method for forming a three-dimensional object, and a three-dimensional printer disclosed in patent document 1 described below, shape data for specifying a shape of the three-dimensional object and surface image data for indicating images of surfaces of the three-dimensional object constitute three-dimensional data, which is divided into a plurality of layers. In the method for forming the three-dimensional object, and the three-dimensional printer, based on cross-sectional slice information of each layer, extruders are caused to extrude inks as build material while moving along a print path in a main scanning direction. Then, after being moved in a sub-scanning direction by a distance corresponding to a single print path, the extruders are caused to extrude the inks as the build material while being moved along a print path in the main scanning direction. In this manner, in the method for forming the three-dimensional object, and the three-dimensional printer, the three-dimensional object is formed by repeating a step of extruding the inks while moving the extruders in the scanning direction and a step of moving the extruders in the sub-scanning direction.